| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.19 085/421] random32: Fix implicit truncation warning in prandom_seed_state() | Date | Mon, 19 Jul 2021 16:48:16 +0200 |
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From: Richard Fitzgerald <rf@opensource.cirrus.com>
[ Upstream commit d327ea15a305024ef0085252fa3657bbb1ce25f5 ]
sparse generates the following warning:
include/linux/prandom.h:114:45: sparse: sparse: cast truncates bits from constant value
This is because the 64-bit seed value is manipulated and then placed in a u32, causing an implicit cast and truncation. A forced cast to u32 doesn't prevent this warning, which is reasonable because a typecast doesn't prove that truncation was expected.
Logical-AND the value with 0xffffffff to make explicit that truncation to 32-bit is intended.
Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20210525122012.6336-3-rf@opensource.cirrus.com Signed-off-by: Sasha Levin <sashal@kernel.org> --- include/linux/prandom.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/prandom.h b/include/linux/prandom.h index cc1e71334e53..e20339c78a84 100644 --- a/include/linux/prandom.h +++ b/include/linux/prandom.h @@ -93,7 +93,7 @@ static inline u32 __seed(u32 x, u32 m) */ static inline void prandom_seed_state(struct rnd_state *state, u64 seed) { - u32 i = (seed >> 32) ^ (seed << 10) ^ seed; + u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL; state->s1 = __seed(i, 2U); state->s2 = __seed(i, 8U); -- 2.30.2
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